Curvature of the spine, whether dorsally convex from kyphosis, forwardly or ventrally convex from scoliosis, or laterally curved from lordosis, can be corrected by an orthopedic surgical technique of simply forcing the curved succession of vertebrae into a straight position and then holding them forcibly in this position. When the ligaments readjust the splinting holding the vetebrae in the new position can be removed and these vertebrae will normally remain in the newly set position.
U.S. Pat. Nos. 2,774,350 of C.S. Cleveland describes an arrangement wherein the spinal processes of the vertebrae being straightened are exposed in a long surgical incision and are secured to respective clips carried on respective threaded rods. The other ends of these rods pass through guides slidable along a main threaded rod lying in the plane of the spinal curvature. The clip-carrying rods have nuts flanking the respective guides so the distance from the main rod to each clip can be changed and set. The distance between adjacent guides on the main rod can be adjusted similarly by means of pairs of nuts flanking the guides. Thus the vertebrae can be pulled into a straight line by shortening the distance between the main rod and the middle clips and simultaneously increasing the distance between guides along the main rod.
Such as arrangement is quite bulky and takes enormous pains to operate, as the surgeon must tighten the various nuts one at a time and only a slight increment each time to create the desired shape, so that the straightening operation is extremely laborious. After the spine is straightened, the entire device must be left projecting through the long incision until the new position has set, that is until the ligaments that hitherto were on the inside of the curve have stretched and those on the outside of the curve have shrunk to their new equal sizes. Obviously these disadvantages make this device less than wholly satisfactory for the surgeon and patient.
It is also known from German Pat. No. 2,649,042 based on an application filed Oct. 28, 1976 by M. B. Ulrich to provide an implantable splint that constitutes part of the device that actually does the straightening, and that can be left in the patient after the spine is straightened to keep the hitherto curved portion of the spine straight, although it is noted of course that the term "straight" is relative only as virtually all parts of the spine are at least gently curved. This splint has a threaded rod that is bendable and extends through a succession of anchors secured to the vertebrae to be straightened. Another implement is employed to initially straighten the succession of vertebrae, with concomitant adjustment of pairs of nuts on the threaded rod that flank the respective anchors. Once the desired straightness is established, the pairs of nuts are tightened against the respective anchors to lock in the set position. This system allows the patient to be closed up after surgery, but still entails considerable work for the initial straightening operation. In addition the rod or rods, which must be flexible in order to follow the original curved line of the anchors, cannot be very rigid, so that occasionally the spine will at least partially revert to its initial nonstraight position.
It is also known to use so-called distraction rods or bars to straighten curved portions of the spine and subsequently to splint the straightened portion in position. Such rods have hooks on their ends that engage over lateral sides of the bony processes of the vertebrae. Normally they are secured in place once the appropriate portion of the spine has been straightened, and are left implanted. Such devices have the disadvantage that they rarely match the exact anatomical shape. In addition, when made adjustable they occasionally come disconnected, requiring corrective surgery to reconnect them.